Controlling A Phacoemulsification Surgical System By Transitioning Between Pulse and Burst Modes

ABSTRACT

Methods of manipulating pulses of ultrasonic energy for use with an ophthalmic surgical device.

RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.11/216,724 filed Aug. 31, 2005.

FIELD OF THE INVENTION

The present invention relates generally to the field of ophthalmicsurgery and, more particularly, to a method of manipulating the shapes,sequences and durations of pulses of ultrasonic energy generated by anultrasound handpiece of a phacoemulsification surgical system.

BACKGROUND

The human eye functions to provide vision by transmitting light througha clear outer portion called the cornea, and focusing the image by wayof a lens onto a retina. The quality of the focused image depends onmany factors including the size and shape of the eye, and thetransparency of the cornea and lens. When age or disease causes the lensto become less transparent, vision deteriorates because of thediminished light that can be transmitted to the retina. This deficiencyis medically known as a cataract. An accepted treatment for cataracts isto surgically remove the cataract and replace the lens with anartificial intraocular lens (IOL). In the United States, the majority ofcataractous lenses are removed using a surgical technique calledphacoemulsification. During this procedure, a thin cutting tip or needleis inserted into the diseased lens and vibrated ultrasonically. Thevibrating cutting tip liquefies or emulsifies the lens, which isaspirated out of the eye. The diseased lens, once removed, is replacedby an IOL.

A typical ultrasonic surgical device suitable for an ophthalmicprocedure includes an ultrasonically driven handpiece, an attachedcutting tip, an irrigating sleeve or other suitable irrigation device,and an electronic control console. The handpiece assembly is attached tothe control console by an electric cable or connector and flexibletubings. A surgeon controls the amount of ultrasonic energy that isdelivered to the cutting tip of the handpiece and applied to tissue bypressing a foot pedal to request power up to the maximum amount of powerset on the console. Tubings supply irrigation fluid to and drawaspiration fluid from the eye through the handpiece assembly.

The operative part of the handpiece is a centrally located, hollowresonating bar or horn that is attached to piezoelectric crystals. Thecrystals are controlled by the console and supply ultrasonic vibrationsthat drive both the horn and the attached cutting tip duringphacoemulsification. The crystal/horn assembly is suspended within thehollow body or shell of the handpiece by flexible mountings. Thehandpiece body terminates in a reduced diameter portion or nosecone atthe body's distal end. The nosecone is externally threaded to accept theirrigation sleeve. Likewise, the horn bore is internally threaded at itsdistal end to receive the external threads of the cutting tip. Theirrigation sleeve also has an internally threaded bore that is screwedonto the external threads of the nosecone. The cutting tip is adjustedso that the tip projects only a predetermined amount past the open endof the irrigating sleeve.

In use, the ends of the cutting tip and the irrigating sleeve areinserted into a small incision in the cornea, sclera, or other location.One known cutting tip is ultrasonically vibrated along its longitudinalaxis within the irrigating sleeve by the crystal-driven ultrasonic horn,thereby emulsifying the selected tissue in situ. The hollow bore of thecutting tip communicates with the bore in the horn that in turncommunicates with the aspiration line from the handpiece to the console.Other suitable cutting tips include piezoelectric elements that produceboth longitudinal and torsional oscillations. One example of such acutting tip is described in U.S. Pat. No. 6,402,769 (Boukhny), thecontents of which are incorporated herein by reference.

A reduced pressure or vacuum source in the console draws or aspiratesemulsified tissue from the eye through the open end of the cutting tip,the cutting tip and horn bores and the aspiration line, and into acollection device. The aspiration of emulsified tissue is aided by asaline solution or other irrigant that is injected into the surgicalsite through the small annular gap between the inside surface of theirrigating sleeve and the cutting tip.

One known technique is to make the incision into the anterior chamber ofthe eye as small as possible in order to reduce the risk of inducedastigmatism. These small incisions result in very tight wounds thatsqueeze the irrigating sleeve tightly against the vibrating tip.Friction between the irrigating sleeve and the vibrating tip generatesheat. The risk of the tip overheating and burning tissue is reduced bythe cooling effect of the aspirated fluid flowing inside the tip.

Some known surgical systems use “pulse mode” in which the amplitude offixed-width pulses can be varied using a controller, such as a footpedal. Other known surgical systems utilize “burst mode” in which eachpulse of a series of periodic, fixed width, constant amplitude pulses isfollowed by an “off” time. The off time can be varied using acontroller. Other known systems use pulses having an initial maximumpower level followed by a lower power level. For example, PublicationNo. PCT/US2004/007318 describes pulses that rise from zero to aninitial, maximum power level, and then subsequently decrease to lowerlevels.

While known surgical systems have been used effectively, they can beimproved by allowing greater control over pulses for use with varioussurgical devices and applications. For example, known systems that usesquare or rectangular pulses typically have power levels that increasevery quickly to a maximum power level. Sharp pulse transitions canreduce the ability to hold and emulsify lens material. Morespecifically, when lens material is held at a tip of an ultrasound handpiece by vacuum, the very fast (almost immediate) ramping of a pulse toa maximum power level can displace or push the lens material away fromthe tip too quickly. This, in is turn, complicates cutting of the lensmaterial. In other words, rapid power transitions can create animbalance between vacuum at the ultrasonic tip that holds or positionsthe lens material and the ability to emulsify lens material.

Other known systems operate at high power levels when less power or nopower would suffice. For example, with rectangular pulses, an initialhigh power level may be needed to provide power to emulsify lensmaterial. However, after the material is pushed away or emulsified,additional power may not be needed. Rectangular pulses that apply thesame amount of power after movement or emulsification of lens materialcan result in excessive heat being applied to tissue, which can harm thepatient.

Further, pulse patterns that are used by some known surgical systems donot adequately reduce cavitation effects. Cavitation is the formation ofsmall bubbles resulting from the back and forth movement of anultrasonic tip. This movement causes pockets of low and high pressure.As the ultrasonic tip moves backwards, it vaporizes liquid due to a lowlocal pressure and generates bubbles. The bubbles are compressed as thetip moves forwards and implode. Imploding bubbles can create unwantedheat and forces and complicate surgical procedures and present dangersto the patient.

Therefore, a need continues to exist for methods that allow pulse shapesand durations to be manipulated for different phacoemulsificationapplications and procedures.

SUMMARY

In accordance with one embodiment of the invention, a method ofgenerating ultrasonic energy for use with an ophthalmic surgical deviceincludes generating pulses having an on-time, a first off-time, and afirst amplitude. The first off-time is greater than the on-time. Themethod includes reducing the first off-time of the pulses and increasingthe amplitude of the pulses from the first amplitude to a secondamplitude when the first off-time is reduced to a pre-determined secondoff-time.

The first off-time can be reduced in response to a controller, such as afoot pedal. The first off-time can be reduced until the foot pedalreaches a pre-determined position corresponding to a certain off-time ofthe pulses, after which the off-time remains constant. The amplitude ofthe pulses is increased after the pre-determined second off-time isabout the same as the on-time in response to the foot pedal. Theoff-time and the amplitude can be adjusted with continuous movement of asingle controller.

In accordance with another embodiment of the invention, a method ofgenerating ultrasonic energy for use with an ophthalmic surgical deviceincludes generating burst mode pulses and transforming burst mode pulsesinto pulse mode pulses in response to a controller.

In accordance with a further embodiment of the invention, a method ofgenerating ultrasonic energy for use with an ophthalmic surgical deviceincludes generating pulse mode pulses and transforming pulse mode pulsesinto burst mode pulses in response to a controller.

Transforming between burst and pulse modes can be performed in responseto movement of the foot pedal and begins after the foot pedal reaches apre-determined position. Burst mode pulses are generated by generatingpulses having an on-time, a first off-time and a first amplitude. Burstmode pulses are transformed into pulse mode pulses by reducing the firstoff-time of the pulses to a second off-time in response to thecontroller. When the second off-time reaches a pre-determined value, theamplitude of the pulses is increased from the first amplitude to asecond amplitude in response to the controller. The pre-determined valuecan be the same as the on-time or another desired value. The on-timeremains constant during the transforming step.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, in which like reference numbers representcorresponding parts throughout and in which:

FIG. 1 illustrates an exemplary phacoemulsification surgical system thatmay be used with various embodiments;

FIG. 2A is block diagram showing components of an exemplaryphacoemulsification surgical system;

FIGS. 2B and 2C illustrate pulses for use with a phacoemulsificationsurgical system;

FIG. 3 illustrates pulses having linear rise and linear decay componentsand a constant maximum amplitude component according to one embodiment;

FIG. 4 illustrates pulses having linear rise and linear decay componentsthat meet at a maximum point according to a further embodiment;

FIG. 5 illustrates a combination of pulses having a rectangular pulseand a pulse having a linear component according to another embodiment;

FIG. 6 illustrates a combination of pulses having a rectangular pulseand a pulse having a linear component according to further embodiment;

FIG. 7 illustrates a combination of pulses having a rectangular pulseand a pulse having a linear component according to yet a furtherembodiment;

FIG. 8 illustrates a combination of pulses having a rectangular pulseand a pulse having a linear component at the same amplitude according toone embodiment;

FIG. 9 illustrates pulses having linear rise and decay components, aconstant amplitude component that has sequentially increasing poweraccording to one embodiment;

FIG. 10 illustrates pulses having linear rise and decay components thatmeet at a maximum point and that have sequentially increasing poweraccording to a further embodiment;

FIG. 11 illustrates a combination of rectangular pulses and pulseshaving a linear component having sequentially increasing power accordingto one embodiment;

FIG. 12 illustrates pulses having linear rise and decay components, aconstant amplitude component and sequentially decreasing power accordingto one embodiment;

FIG. 13 illustrates pulses having linear rise and linear decaycomponents that meet at a maximum point and having sequentiallydecreasing power according to a further embodiment;

FIG. 14 illustrates a combination of rectangular pulses and pulseshaving a linear component and that have sequentially decreasing poweraccording to another embodiment;

FIG. 15 illustrates known fixed burst mode pulses;

FIG. 16 illustrates known linear burst mode pulses;

FIG. 17 illustrates known pulse mode pulses;

FIG. 18 illustrates continuous transformation of burst mode pulses topulse mode pulses in response to a controller according to oneembodiment;

FIG. 19 illustrates continuous transformation of pulse mode pulses toburst to mode pulses in response to a controller according to anotherembodiment;

FIG. 20 illustrates multi-segment rectangular pulses having two pulsesegments with increasing amplitude according to yet another embodiment;

FIG. 21 illustrates a multi-segment rectangular pulse according to analternative embodiment having three pulse segments with increasingamplitude;

FIG. 22 illustrates packets of pulses of ultrasonic energy shown in FIG.10; and

FIG. 23 illustrates packets of pulses of ultrasonic energy shown in FIG.13.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

This specification describes embodiments of methods of manipulatingpulses of ultrasonic energy to control a surgical system for use in, forexample, phacoemulsification surgery. Embodiments can be implemented oncommercially available surgical systems or consoles through appropriatehardware and software controls. FIGS. 1 and 2 illustrate exemplarysurgical systems.

FIG. 1 illustrates one suitable system and represents the INFINITI®Vision System available from Alcon Laboratories, Inc., 6201 SouthFreeway, Q-148, Fort Worth, Tex. 76134. FIG. 2A illustrates an exemplarycontrol system 100 that can be used with this system.

The control system 100 is used to operate an ultrasound handpiece 112and includes a control console 114, which has a control module or CPU116, an aspiration, vacuum or peristaltic pump 118, a handpiece powersupply 120, an irrigation flow or pressure sensor 122 and a valve 124.Various ultrasound handpieces 112 and cutting tips can be utilizedincluding, but not limited to, handpieces and tips described in U.S.Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583;4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and5,359,996, the contents of which are incorporated herein by reference.The CPU 116 may be any suitable microprocessor, micro-controller,computer or digital logic controller. The pump 118 may be a peristaltic,a diaphragm, a Venturi or other suitable pump. The power supply 120 maybe any suitable ultrasonic driver. The irrigation pressure sensor 122may be various commercially available sensors. The valve 124 may be anysuitable valve such as a solenoid-activated pinch valve. An infusion ofan irrigation fluid, such as saline, may be provided by a saline source126, which may be any commercially available irrigation solutionprovided in bottles or bags.

In use, the irrigation pressure sensor 122 is connected to the handpiece112 and the infusion fluid source 126 through irrigation lines 130, 132and 134. The irrigation pressure sensor 122 measures the flow orpressure of irrigation fluid from the source 126 to the handpiece 112and supplies this information to the CPU 116 through the cable 136. Theirrigation fluid flow data may be used by the CPU 116 to control theoperating parameters of the console 114 using software commands. Forexample, the CPU 116 may, through a cable 140, vary the output of thepower supply 120 being sent to the handpiece 112 and the tip 113 thougha power cable 142. The CPU 116 may also use data supplied by theirrigation pressure sensor 122 to vary the operation of the pump 118and/or valves through a cable 144. The pump 118 aspirates fluid from thehandpiece 112 through a line 146 and into a collection container 128through line 148. The CPU 116 may also use data supplied by theirrigation pressure sensor 122 and the applied output of power supply120 to provide audible tones to the user. Additional details concerningsuch surgical systems can be found in U.S. Pat. Nos. 6,179,808 (Boukhny,et al.) and 6,261,283 (Morgan, et al.), the entire contents of which areincorporated herein by reference.

The control console 114 can be programmed to control and manipulatepulses that are delivered to the handpiece 112 and, in turn, control thepower of the pulses of the handpiece that is used during surgery.Referring to FIGS. 2B and 2C, the pulses are generated in packets or inon periods and off periods. In the illustrated example, to the pulseshave a 50% duty cycle. Indeed, various on-times, off-times and dutycycles can be used for different applications.

The following description assumes that a maximum power level of 100% isthe maximum attainable power (i.e., maximum stroke or displacement ofthe ultrasonic tip). In other words, 50% power refers to half of themaximum attainable power. Power levels are represented as a percentage(%) of the maximum attainable power. Embodiments of pulse manipulationthat can be used with the exemplary phacoemulsification surgical systemdescribed above are illustrated in FIGS. 3-21, which can be organized asmicro-bursts or packets of pulses, as shown in FIGS. 2B and 2C. Thepackets or bursts of pulses are provided to the ultrasound handpiece,which generates a generally corresponding output at the ultrasonic tip.

Referring to FIG. 3, according to one embodiment, one or both of therise and decay components 310 and 312 of each pulse 300 can beprogrammed separately from a natural rise and natural decay. For examplerise and decay components 310 and 312 can be programmed with linearand/or non-linear functions separately from natural rise and decay timesthat occur due to switching an amplifier on and off to generate pulses.Persons skilled in the art will appreciate that some pulses (e.g.,square and rectangular pulses) are typically represented as “ideal”square or rectangular pulses having immediate and sharp transitionsbetween low and maximum power levels. In practice, however, such pulseshave natural rise and decay times, e.g., exponential rise and decaytimes, which are caused by a load or impedance. For example, typicalnatural decay times can be about 4 milliseconds (ms). Embodiments, incontrast, are directed to controlling linear rise and linear decay timesseparately from natural transitions that are caused by switching anamplifier on and off by setting or programming the rise and/or decayfunctions.

Controlling the rise and decay components 310 and 312 and rise and decaytimes 312 and 322 provides advantageously allows different pulseconfigurations to be generated for particular surgical applications andsystems. For example, pulses having programmed rise components 310 thatgradually increase in power allow the lens material to be positionedmore accurately. Gradual power transitions, for example, do notprematurely push the lens material away from the tip of the handpiece.In contrast, known systems using pulses having sharp minimum to maximumtransitions may inadvertently push lens material away from the tip tooquickly, thus complicating the surgical procedure. Accordingly, pulsesthat include programmed rise components can improve the positioning andcutting of lens material and the effectiveness of surgical procedures.Further, programming decay components and pulse times allows less energyto be delivered to the eye, resulting in less heating of the tissue.

According to one embodiment, the programmed rise and/or decay componentis programmed according to a linear function. In the embodimentillustrated in FIG. 3, each pulse 300 is programmed with two linearcomponents—a linear rise component 310 and a linear decay component 320.The linear rise component 310 increases from a first amplitude to asecond amplitude. An intermediate component 330 extends between thelinear components 310 and 320 at a second amplitude. The decay component330 decreases from the second amplitude to a third amplitude.

The linear rise component 310 has a linear rise time 312, the lineardecay component 320 has a linear decay time 322, and the maximumamplitude component 330 has a maximum amplitude or active or “on” time332. Linear rise and linear decay times 312 and 322 can vary dependingon the maximum power level of a pulse since more time is typicallyrequired to reach higher power levels.

In one embodiment, the linear rise time 312 can be programmed to beabout 5 ms to about 500 ms. If a pulse must reach 100% power, theduration of the linear rise time 312 may be longer. However, if thepulse must reach less than 100% power, then the linear rise time 312 canbe shorter, e.g. less than or about 5 ms. Linear rise time 312 durationsmay increase with increasing power levels and can be appropriatelyprogrammed using the control console 114. If necessary, the rate atwhich the linear component increases can be limited to protect powercomponents, such as an amplifier.

According to one embodiment, the linear decay time 322 can be programmedto be about 5 ms to about 500 ms. In one embodiment, the liner decaytime 322 is programmed using the control console 114 so that powerdecays linearly and about 70% of the power dissipates in about 2 ms, andabout 98% of the power dissipates in about 4 ms. The linear decay time322 may be longer than, about the same as, or shorter than the linearrise time 312. For example, FIG. 3 illustrates the decay time 322 beinglonger than the rise time 312. The linear decay time 322 can be longeror slower than a natural decay time. The rise and decay rates may alsobe the same so that the pulse is symmetrical and has both programmedrise and decay components.

The maximum amplitude or active or “on” time 332 can vary with differentapplications. The maximum amplitude time can be about 5 ms to about 500ms. In the illustrated embodiment, the intermediate component 330 has aconstant amplitude (at the second amplitude). In an alternativeembodiment, the duration of the maximum amplitude time can be less than5 ms depending on, for example, required power and resulting heatconsiderations. In further alternative embodiments, the amplitude mayvary across the intermediate component 330, e.g., increase or decreasebetween the first and second components 310 and 320.

In the illustrated embodiment, the rise component 310 begins at anon-zero level. In an alternative embodiment, the rise component 310 canbegin at a zero level. The initial power level may depend on theparticular surgical procedure and system configuration. Similarly, thedecay component 320 can end at a zero or non-zero power level. FIG. 3illustrates the first and third amplitudes being about the same. Inalternative embodiments, they can be different. For example, the thirdamplitude at the end of the decay component 320 can be greater than thefirst amplitude.

In an alternative embodiment, the programmed rise and/or decay componentcan be a non-linear component. A non-linear component can be programmedaccording to logarithmic, exponential and other non-linear functions.For purposes of explanation, not limitation, FIG. 3 illustrates linearrise and decay components. However, one or both of the rise and decaycomponents can be programmed with a non-linear function.

Referring to FIG. 4, according to an alternative embodiment, a pulse 400is programmed with linear rise and linear decay components 310 and 320that meet at a maximum point 410 at a second amplitude rather thanhaving an intermediate component 330, as shown in FIG. 3. In theillustrated embodiment, the programmed rise and decay times 312 and 322are equal. The linear rise and decay components 310 and 320 meet at amidpoint. In alternative embodiments, as discussed above with respect toFIG. 3, linear rise and decay times 312 and 322 can be programmed to beabout 5 ms to about 500 ms. Thus, the rise and decay times may not beequal, and the maximum point 410 may not be a midpoint.

Referring to FIGS. 5-8, in alternative embodiments, pulses having one ormore linear and/or non-linear components can be combined with otherpulses and pulse patterns. For purposes of explanation, not limitation,FIGS. 5-8 illustrate pulses having programmed linear components,however, one or more programmed linear components can be replaced with aprogrammed non-linear component.

FIG. 5 illustrates a sequence or combination 500 of pulses having afirst rectangular pulse 510, a second rectangular pulse 520, a pulse 530having a linear decay component, a pulse 540 having a linear risecomponent and a pulse 550 having linear rise and linear decaycomponents, similar to the pulse shown in FIG. 4.

FIG. 6 illustrates a sequence or combination 600 of pulses according toanother embodiment that includes a pulse 610 having linear rise anddecay components and an intermediate component, similar to the pulseshown in FIG. 3, a rectangular pulse 620, a rectangular pulse 630 havinga longer duration than pulse 620, a pulse 640 having a linear decaycomponent and a pulse 650 having a linear rise component.

FIG. 7 illustrates yet a further embodiment of a sequence or combination700 of pulses that includes a pulse 710 having a linear decay component,a multi-segment rectangular pulse 720 having decreasing amplitude, apulse 730 having a linear decay component, a pulse 740 having a lineardecay component and a 750 pulse having both linear rise and linear decaycomponents, similar to the pulse shown in FIG. 4, and anotherrectangular pulse 760.

FIG. 8 illustrates a further alternative embodiment of a sequence orcombination 800 of pulses having the same maximum amplitude and at leastone pulse having a linear component. In particular, FIG. 8 illustrates apulse 810 having a linear decay component, a multi-segment rectangularpulse 820 having decreasing amplitude, a pulse 810 having a linear decaycomponent, a pulse 840 having a linear decay component, a pulse 850having both linear rise and decay components, similar to the pulse shownin FIG. 4, and a rectangular pulse 860.

As illustrated in FIGS. 5-8, each pulse in a packet of pulses can havean attribute that differentiates it from other pulses, e.g., based ondifferent amplitude, duration, shape, number of programmed linearcomponents and/or power. For example, pulse combinations can have pulseshaving different powers, amplitudes, shapes and durations. Further,pulse combinations can have different numbers of pulses, differentnumbers of rectangular and square pulses, different numbers of pulseshaving linear components, different numbers of pulses having one linearcomponent, numbers of pulses having two linear components, and differentnumbers of pulses having two linear components and a constant amplitudecomponent. Thus, embodiments surgeons to customize pulses to suiteparticular surgical procedures and phacoemulsification systems.

As shown in FIG. 5-8, the rectangular pulses and pulses having one ormore linear component, can be placed in different positions andsequences, e.g., and at the beginning or end of a pulse sequence, orsomewhere in between. The order of rectangular (or other shaped pulses)and pulses having a linear component can be altered depending on thesurgical application and the system used. Certain pulses may be groupedtogether or comingled with other types of pulses.

For example, referring to FIG. 5, rectangular pulses 510 and 520 aregrouped together and pulses 520, 530 and 540 having a linear componentare grouped together. In an alternative embodiment, one or morenon-rectangular pulses can be between the rectangular pulses so that therectangular pulses are comingled with different types pulses. Similarly,one or more pulses that do not include a linear component can be placedbetween the pulses having a programmed linear component.

Referring to FIGS. 9-14, in alternative embodiments, pulses having aprogrammed linear component are included in a pattern of pulses in whicheach pulse has sequentially decreasing power or increasing power. FIGS.9-11 illustrate pulse sequences in which each pulse has sequentiallyhigher power, and FIGS. 12-14 illustrate pulse sequences in which eachpulse has sequentially decreasing power.

Referring to FIG. 9, an alternative embodiment includes a sequence orcombination 900 of pulses that includes pulses 910, 920, 930, 940 and950, each of which is similar to the pulses shown in FIG. 3. Eachsuccessive pulse has a higher power (P1-P5) than a prior pulse. Forexample, pulse 930 has a power P3, which is greater than the power P2 ofpulse 920.

FIG. 10 illustrates an alternative embodiment in which a sequence orcombination 1000 of pulses includes pulses 1010, 1020, 1030, 1040, and1050, each of which is similar to the pulses shown in FIG. 4. Eachsuccessive pulse has a higher power than a prior pulse.

FIG. 11 illustrates yet a further embodiment in which a sequence orcombination 1100 of pulses includes pulses of various shapes and sizes,including rectangular pulses and at least one pulse having a linearcomponent. Each successive pulse has a higher power than a prior pulse.A sequence or group of pulses having an initial low power level andsubsequent increasing power levels may be useful to effectively hold andcontrol lens material at a tip of an ultrasound handpiece, whilegradually increasing power to emulsify lens material.

Referring to FIG. 12, according to another embodiment, a sequence orcombination 1200 of pulses includes pulses 1210, 1220, 1230, 1240 and1250, each of which is similar to the pulse shown in FIG. 3. Each pulseincludes a programmed linear rise component 310 and a programmed lineardecay component 320. Each pulse has reduced power relative to a priorpulse. For example, pulse P3 has less power than pulse P2, and pulse P4has less power than pulse P3.

In an alternative embodiment, referring to FIG. 13, a sequence or groupof pulses includes pulses 1310, 1320, 1330, 1340 and 1350. Each pulse issimilar to the pulse shown in FIG. 4, and each pulse has reduced powerrelative to a prior pulse.

FIG. 14 illustrates yet a further embodiment in which a sequence orcombination 1400 of pulses 1410, 1420, 1430, 1440 and 1450 havingreduced power over time. The combination 1400 includes pulses havingdifferent shapes and sizes, including rectangular pulses and pulseshaving a linear component.

Referring to FIGS. 15-19, alternative embodiments are directed totransforming pulses between different pulse modes in response to acontroller, such as a foot pedal or foot switch. According to oneembodiment, pulses are transferred between burst and pulse modes. Pulsepatterns are shown relative to four foot pedal positions, which may ormay not be defined by a detent or position indicator. Persons skilled inthe art will appreciate that a foot pedal or switch can have othernumbers of positions, and that the transitions described herein can beperformed by pressing and releasing the foot pedal.

Referring to FIG. 15, “burst” mode provides a series of periodic, fixedwidth, constant amplitude pulses 1500 of ultrasonic power, each of whichis followed by an “off” time 1510. The off time 1510 between pulses 1500is controlled by the surgeon's input by moving or pressing the footpedal. In other words, in burst mode, each pulse 1500 has a fixed “on”time 1520, and a variable “off” time 1510, and the “off” time 1510 isadjusted based on the user's manipulation of the foot pedal. Burst modepulses can have active times of about 5 ms to about 500 ms. The spacingbetween bursts or the “off-time” can be about 0 ms (when the foot pedalis fully depressed and power is continuous) to about 2.5 seconds. Theoff-time can depend on the application and system, for example, thedesired amount of cooling or heat dissipation that may be required.Burst mode pulses may be “fixed burst” mode pulses as shown in FIG. 15or, alternatively, be “linear burst” mode pulses as shown in FIG. 16. Infixed burst mode, pressing the foot pedal decreases the off-time 1510,while the amplitude of the pulses remains constant. In linear burstmode, pressing the foot pedal decreases the off-time 1500 and, inaddition, adjusts the amplitude. In the illustrated embodiment, pressingthe foot pedal increases the amplitude. Thus, in both fixed and linearburst modes, the power “Off” time 1510 can be adjusted, and theamplitude of pulses may or may not be adjusted.

More particularly, FIGS. 15 and 16 illustrate a foot pedal in fourpositions. The off time 1510 decreases when the foot pedal is initiallyat Position 1 and pressed further to Position 2. The number of fixedwidth, constant amplitude pulses 1500 increases as the foot pedal ispressed. As the foot pedal is pressed from Position 2 to Position 3, theoff time 1510 eventually reaches a pre-determined off time 1520, e.g.,the on time 1520 or another suitable time. Pressing the foot pedalfurther from position 3 to position 4 reduces the off time 1510 to zero,i.e., a 100% on-time 1520 (continuous mode). A similar process isillustrated in FIG. 16, except that the pulses are linear burst modepulses, and the amplitude of the pulses also increases as the foot pedalis moved among different positions.

Referring to FIG. 17, in “pulse” mode, the amplitude of fixed-widthpulses 1700 changes according to the position of the foot pedal. In theillustrated embodiment, the amplitude increases by pressing the footpedal.

Referring to FIGS. 18 and 19, alternative embodiments are directed totransforming pulses between burst and pulse modes in response tomovement of the foot pedal. FIG. 18 illustrates transitioning from burstmode to pulse mode. The foot pedal is pressed from Position 1 toPosition 2 to decrease the off time 1510. The off-time decreases furtherwhen the foot pedal is pressed from Position 2 to Position 3. The numberof fixed width, constant amplitude pulses in a period of time increasesas the foot pedal is pressed further. As the foot pedal is pressedfurther, the off time 1510 eventually reaches a pre-determined value,such as the on time 1520 or another suitable value. In the illustratedembodiment, the pre-determined value is equal to the on-time 1520. Thepulse amplitude is then adjusted after the off time 1510 is the same asthe on time 1520 (or another suitable value), thereby increasing energyis generated by the handpiece, and transforming pulses from burst modeto pulse mode pulses.

Referring to FIG. 19, in an alternative embodiment, pulses aretransformed from pulse mode to burst mode pulses. If the system isinitially in pulse mode and the foot pedal is pressed to position 4,releasing the foot pedal initially decreases the amplitude of thepulses. After the amplitude reaches a pre-determined amplitude,releasing the foot pedal further results in adjusting the burst mode andincreasing the power “Off” time 1510, thereby providing fewer fixedwidth pulses 1500 in a given time and less power to the ultrasonic tip113, in order to cool the tip 113.

As shown in FIGS. 18 and 19, a surgeon can advantageously switch betweenburst mode and pulse mode pulses by manipulating a single controller,e.g., by pressing and releasing the foot pedal. This arrangement isparticularly beneficial since these transformations can be achievedwithout the interruptions and adjustments that are otherwise associatedwith changing to different pulse modes, e.g., adjusting parameters on adisplay screen or interface. Instead, embodiments advantageously allowcontinuous pulse transitions by pressing and releasing the foot pedal aspart of a natural and continuous motion of the surgeon's foot, therebysimplifying the configuration and operation of surgical equipment andsimplifying surgical procedures.

Referring to FIG. 20, in a further alternative embodiment, the amount ofpower of each pulse can be gradually increased by utilizing a multi-stepor multi-segment pulse 2000. Persons skilled in the art will appreciatethat a multi-segment pulse can have two, three, four and other numbersof segments. Thus, the two-segment pulse shown in FIG. 20 is providedfor purposes of illustration, not limitation.

In the illustrated embodiment, a first step 2010 has less power than asubsequent step 2020. For example, as shown in FIG. 20, a first pulsesegment 2010 is at a first amplitude for a pre-determined time, followedby a second pulse segment 2020 at a second amplitude for apre-determined time. Configuring a multi-segment pulse to provide agradual transition from low power to higher power provides the abilityto hold and emulsify lens material more accurately in contrast to abrupttransitions from low to maximum power levels such as in a typicalsquare, which can inadvertently move lens material away from the tipduring cutting of the lens material Referring to FIG. 21, in alternativeembodiments, a multi-segment pulse 2100 may have more than two segmentsof increasing amplitude. In the illustrated embodiment, a pulse hasthree pulse segments 2110, 2120 and 2130. Other pulses may have four,five and other numbers of pulse segments as needed.

The different pulses and pulse patterns described above are pulses ofultrasonic energy that can be delivered in packets to transducerelements of the handpiece. For example, as shown in FIGS. 2B and 2C,ultrasonic energy is delivered to piezoelectric elements as intermittentpackets of pulses that are separated by an off period. The pulsespatterns according to alternative embodiments of the invention describedabove are delivered to piezoelectric elements of an ultrasound handpieceduring these “on” times and within these packets.

For example, FIG. 23 illustrates packets of pulses of ultrasonic energyhaving sequentially increasing power, as shown in FIG. 10. As a furtherexample, FIG. 24 illustrates packets of pulses of ultrasonic energyhaving sequentially decreasing power, as shown in FIG. 13. Personsskilled in the art will appreciate that a packet may have one ormultiple groups of pulses, and that a packet may end at the end of agroup of pulses or in the middle of a group of pulses. For example,FIGS. 22 and 23 illustrate a packet ending with the second pulse in agroup of pulses. The packet may also end with the last pulse in thegroup of pulses. Accordingly, FIGS. 22 and 23 are provided for purposesof illustration, not limitation. Persons skilled in the art will alsoappreciate that the embodiments of pulses described in thisspecification are not required to be framed or organized in packets inorder to control the ultrasound handpiece.

Although references have been made in the foregoing description tovarious embodiments, persons of skilled in the art will recognize thatinsubstantial modifications, alterations, and substitutions can be madeto the described embodiments without departing from the scope ofembodiments.

1. A method of generating ultrasonic energy for use with an ophthalmicsurgical device, the method comprising: generating pulses having anon-time, a first off-time, and a first amplitude, the first off-timebeing greater than the on-time; reducing the first off-time of thepulses; and increasing the amplitude of the pulses from the firstamplitude to a second amplitude when the first off-time is reduced to apre-determined second off-time.
 2. The method of claim 1, whereinreducing the first off-time comprises reducing the first off-time inresponse to a controller.
 3. The method of claim 2, wherein thecontroller is a foot pedal and is reducing the first off-time comprisesreducing the first off-time in response to movement of the foot pedal.4. The method of claim 3, wherein reducing the first off-time comprisesreducing the first off-time until the foot pedal reaches apre-determined position, after which the off-time remains constant. 5.The method of claim 1, wherein increasing the amplitude of the pulsesfrom the first amplitude to the second amplitude begins after thepre-determined second off-time is about the same as the on-time.
 6. Themethod of claim 1, wherein increasing the amplitude comprises increasingthe amplitude from the first amplitude to the second amplitude inresponse to a controller.
 7. The method of claim 6, wherein thecontroller is a foot pedal and the first amplitude is increased inresponse to movement of the foot pedal.
 8. The method of claim 7,wherein increasing the amplitude of the pulses from the first amplitudeto the second amplitude begins after the foot pedal is moved to apre-determined position.
 9. The method of claim 1, wherein thecontroller is a foot pedal and continuous movement of the foot pedalinitially reduces the first off-time and then increases the amplitudefrom the first amplitude to the second amplitude.
 10. The method ofclaim 1, wherein the first off-time and the first amplitude areadjustable in response to the same controller.
 11. The method of claim1, wherein the on-time remains substantially constant during the stepsof reducing the first off-time and increasing the first amplitude. 12.The method of claim 1, wherein generating pulses comprises generatingrectangular pulses.